Each of the above references disclosed a thickened aqueous scouring cleanser containing abrasives and a bleach source. The present invention includes certain components and features which are common to the cleansers of the above noted references. Accordingly, portions of the following disclosure are similar to portions of the above noted references.
As was also noted in the above reference, various heavy duty cleansers have been developed in the prior art for removing a variety of soils and stains from hard surfaces. The nature of those heavy duty cleansers is summarized below with respect to prior art references in which representative cleansers are further described.
Initially, U.S. Pat. No. 3,985,668 issued to Hartman, describes a combination of perlite (an expanded silica abrasive) and a colloid-forming clay in combination with a hypochlorite bleach, a surfactant and a buffer with abrasives being suspended in the combination. A clay thickened system of this type tends to set up or harden upon storage due to the false body nature of the thickeners. Such products require shaking before use in order to break down the false body structure and make the product flowable.
Other prior art cleansers have been formulated in an attempt to suspend abrasives using only inorganic colloid thickeners. However, in such products, syneresis has commonly been a problem in that a solids portion of the cleansers has substantially separated from the liquid portion. This layering effect resulting from syneresis not only detracts from the esthetic appearance of the product but also requires that the product be shaken or agitated prior to use in order to achieve uniform dispersion of its cleaning components throughout the composition.
One way of alleviating syneresis problems in the prior art has been through the use of perlite or perlite type material with specified particle sizes as defined in U.S. Pat. No. 3,985,668 issued to Hartman and also noted above.
In addition to the problem of syneresis, it is also necessary to compound such products in order to condition them for maintaining particulate solids such as abrasives in suspension. As is well known in the art, abrasives are commonly employed in such products in order to enhance their ability to scour or clean hard surfaces.
In the prior art, high levels of surfactants have been employed to form a plastic rheology for achieving suspension of abrasives and the like. However, the presence of high levels of surfactants in turn commonly exhibits a detrimental effect on hypochlorite bleach stability. For example, U.S. Pat. No. 4,352,678, issued to Jones et al, disclosed cleanser compositions thickened with mixed surfactants for the purpose of suspending abrasives, the cleansers also incorporating a source of hypochlorite bleach. As disclosed by this particular reference, relatively large amounts of surfactants were incorporated into the cleansers in order to satisfactorily suspend the abrasives. However, the use of relatively large amounts of surfactants had the unfortunate disadvantage of causing poor hypochlorite bleach stability in terms of half-life stability at 50.degree. C. even with relatively low levels of hypochlorite (0.5% sodium hypochlorite initial level).
For the purposes of the present invention and also in accordance with the above noted reference, half-life stability is defined as the amount of time it takes for 50% of the initial amount of bleach present in a given composition to decompose.
Other prior art references have also disclosed cleansers in which clay was used as a thickener and for suspending abrasives. However, such clay-thickened cleansers often have a tendency to set up or harden, often in a relatively short time. At the same time, typical clay-thickened cleansers in the prior art also tend to exhibit significant syneresis problems.
Other related efforts in the prior art include for example U.S. Pat. No. 4,337,163, issued to Schilp, which disclosed a hypochlorite bleach product thickened with a combination of amine oxides and anionic surfactants. However, the thickened bleach product disclosed by Schilp contained neither clay now abrasive particles requiring suspension in the manner disclosed above. Moreover, the high amount of surfactants may lead to hypochlorite stability.
U.S. Pat. No. 3,956,158 (and corresponding British Pat. No. 1,418,671), issued to Donaldson, disclosed an abrasive-containing bleach thickened with insoluble detergent filaments. As was also noted in U.S. Pat. No. 4,352,678, referred to above, compositions such as those disclosed in the Donaldson patent have also exhibited numerous disadvantages, including low detergency and lack of physical and chemical stability at higher temperatures.
In the copending reference initially noted above, a very effective cleanser composition was described and included both abrasives and hypochloride bleach. A creamy or smoothly flowable consistency and plastic rheology resulting in continuously flowable characteristics of the composition resulted from the use of one or more selected surfactants together with hydrated aluminum oxide as a thickener which functioned in combination with an electrolyte/buffer to achieve the desired plastic rheology noted above. At the same time, the composition of the copending reference exhibited minimal or essentially no syneresis or phase separation. Thus, even after relatively long periods of storage, the composition of the copending reference did not require shaking or agitation. Rather, the product was readily pourable and exhibited uniform distribution of its various components throughout the composition.
In connection with the present invention, it was found that certain modifications tended to be necessary in connection with the composition of the copending reference, for example, to satisfy environmental requirements in certain areas prohibiting the use of phosphates in such cleaning products. Replacing phosphates in the cleaning composition with other electrolyte/buffers, particularly silicates, resulted in more thixotropic characteristics. Accordingly, there was found to remain a need for a product similar to that disclosed by the copending reference noted above while satisfying environmental requirements by the absence of phosphates and also exhibiting a consistency similar to the plastic rheology of the copending reference.
It will also be apparent that such a plastic rheology is desirable in a number of other cleanser products in addition to the abrasive containing scouring cleansers of the type disclosed above in order to take advantage of desirable resulting characteristics such as uniform distribution of components and smooth flowing or pourable qualities in products even after they have been standing for relatively long periods of time.
Accordingly, there has been found to remain a need for a thickened aqueous cleanser having a plastic rheology and being capable of use without the need for prior shaking or agitation. At the same time, there has been found to remain a need for thickened hard surface cleansers having characteristics such as those noted above while also being capable of suspending abrasives and/or containing bleaches while exhibiting little or no syneresis over time and also having long-term bleach stability.